I think that there both about the same quality, both can be ordered as rebuildable. The denton has 7 settings and the PEP has 3. PM schmitthead if you want a denton, he has some of the best prices around.
go with the denton. had a pep on my yfz and it didnt last. i am now using the denton off my 250r on the yfz and it works way better and that one is a couple years old. i bought a new denton for the 450r and very happy with it as well